During its manufacture, an individual product usually undergoes a sequence of operations, some of which may include different tests and or inspections. For example, a complex electronic system may undergo one or more electrical tests, as well as one or more visual inspections during its manufacture. Under ideal circumstances, each manufactured product will pass each test and inspection to which the product has been subjected. Unfortunately, no manufacturing process is ever perfect. Indeed, with very complex products that require a complicated sequence of manufacturing operations, errors do occur during manufacturing, causing one or more products to fail one or more tests/inspections. In some instances, a test/inspection failure may be correctable by a repair. Once repaired, the product is re-tested and re-inspected. If the repair is successful, then the product should pass the previously failed test/inspection. Should the repair be unsuccessful, the product must undergo another repair followed by a subsequent re-test/reinspection.
Some times, the nature of the test/inspection failure will dictate the type of repair that is made. However, in many instances, the test/inspection performed on the product may not provide sufficient information to enable an operator to determine the exact type of repair needed to cure the defect. Thus, an operator undertaking repair of a defective product must further diagnose the product before repairing it, thereby increasing the time, and hence the cost, associated with manufacture of the product. Over time, an experienced operator may learn that a certain repair is more likely to cure a product that has failed a particular test/inspection. Such an operator will likely enjoy a high success rate, which is inversely related to the number of repairs an operator undertakes on a given product to render it operable. Clearly, if all operators had a knowledge of which repairs were likely to be more successful, then the overall repair success rate would increase, thereby decreasing manufacturing costs.
In some instances, a particular sequence of manufacturing operations may yield a defective product even if all of the operations are performed correctly. This is because one of the manufacturing operations may interfere with another owing to the order in which the operations were performed. While the defect may be curable by a repair, it is more desirable to avoiding making any repairs at all. However, for a complex product that undergoes many operations during its manufacture, an improper sequence of operations may not be readily apparent, even to a trained manufacturing engineer.
Thus, there is a need for a technique for analyzing a sequence of manufacturing operations, particularly for the purpose of modifying the sequence to improve the manufacturing process.